20 hp motor lower unit stuck

just picked up a motor from a deceased friends dad and am trying to get it running. it is a 71 mercury 20 hp model 200. motor is in excellent shape but has been sitting up for 5-7 years. couldnt get the motor to turn over (felt like a stuck piston) dropped the lower unit and that was my problem. Lower unit is stuck and now i dont know what to do with it. Can it be unstuck or does it have to be replaced? I drained everything out of it and refilled it hoping it will seep into the right placed and free it up, but anyone have any other ideas? how much will this thing cost me to have replaced if I can find one? What other year models will fit on it (or will any others) thanks in advance guys

Re: 20 hp motor lower unit stuck

There should be quite a few years of lower units that will fit that motor--probably late 1960's to late 1970's. Since this LU is locked up, why not take it apart and see what's up with it? If it's been in salt water, though, it may be toast. Get a manual, take the water pump off, and take it from there. You can fabricate the special tools needed.<br /><br />You will find these lower units on eBay ranging from $30 for one with problems (you already have one of these) to $175 for one that is in good shape, checked out, with new seals, etc. There is one right now with a $169 buy it now price I believe.<br /><br />I'm thinking the 1971 has an odd and expensive ignition system, using points and a CDI box. You might make sure the power head is in working condition before you spend a lot on the lower. That CDI box is around $200. Parts available at www.oldmercs.com.<br /><br />On your lower unit, will it shift and can you turn either shaft (driveshaft or propshaft)? If the LU is in forward, the prop should turn clockwise without turning the driveshaft and will make a ratcheting sound. In nuetral, it should turn both ways. In reverse, it will only turn a little bit each way without the drive shaft turning.

Re: 20 hp motor lower unit stuck

the prop will do exactly as you described. As for the LU on Ebay, I have already spoken to him. He only lives an hour or so away so I have no problem heading that way to pick it up. How would I go about testing the power pack?

Re: 20 hp motor lower unit stuck

To test the power pack you need to check for spark. This can be done by removing the plugs, grounding them, and pulling the rope to verify that you have a good strong spark. You can also check compression which does not have a specific number to check for but which should be within 10% of each other on the two cylinders. And see how the motor feels as you turn the crank with the plugs out--should be nice and smooth.<br /><br />If you buy that lower unit, load up your motor and take it with you to make sure it fits.

Re: 20 hp motor lower unit stuck

If your propshaft turns but not the driveshaft, remove the water pump and see if that makes any difference. However, these symptoms could mean just that the driveshaft bearing is bad, or it could be the gears or propshaft bearings are bad. Keep us posted!

Re: 20 hp motor lower unit stuck

is there a place I can buy a manual online (like a PDF file) I am going to the lake this weekend and would like to have it ready by then. I dont want to have to wait for it to get shipped. Going by the serial number it looks like it may be a 74 model. serial number starts with 388. Is the water pump easy to get out? looking at it I cant see anyway short of pulling it out to make it come. And since I dont want to tear anything up I am just serching! Thanks for all the help, you have been great!

Re: 20 hp motor lower unit stuck

scratch all that... Since I had planned on buying a new lower unit I went ahead and put the old one in the vice and gave it a twist. That freed it up! cleaned it up and 2 hours later I was on the water. Took it to the in-laws pond and messed with it and got it to run/idle. put it in gear and idled a little, looks like it is going to work out. thanks

Re: 20 hp motor lower unit stuck

Great news! Now--change the lower unit oil, save the oil you drain out and check it for water and metal. Let us know what you find. Put a new impeller in the water pump, and make sure you have a good stream of water out the tell tale. Water pump impellers get hard and fall apart--they are made of rubber. If the water pump isn't cooling the motor, it will fry. <br /><br />Check the FAQ section of this board and read the post about waking a sleeping motor. Lots of good info there. Take good care of that motor and it may well run a long time.

Re: 20 hp motor lower unit stuck

one last question. I should have read before I dropped the lower unit.... When I pulled the LU I had it in FWD not in neutral. Now my neutral is where reverse should be and Forward is where neutral should be and I have no reverse. How do I fix it? I am going to get a new impeller tomorrow. The few minutes that I ran it today I had minimal water flowing out. The impeller is still in good shape, but Im going to replace anyways. Thanks

Re: 20 hp motor lower unit stuck

I found a repair manual for my '72 200 (20 hp) at the public library and copied it. I'v enever changed out a LU but I recall in fo about lining up the gears on reinstallation. The lever system inside the motor is fairly complicated. Also my old one jumped into gear too easily; I "solved" by putting controls on it but the factory spring clip is very weak.<br />Also I had what appeared to be a fuel flow problem--stalled out when in gear, or wouldn't start unless revved up in forward (!) and although it acted like fuel, it was worn wires that hit the block when the stator moved on acceleration. I'd replace all the outside wires next time you have it in the shop.

Re: 20 hp motor lower unit stuck

1970's Mercs had really bad wires, the insulation falls off. Bluehull is correct, give them a good look-see.<br /><br />Impeller can be intact but hardened, and will not work properly, particularly at low speed.<br /><br />Put the LU in neutral, drop the lower, put the shifter in neutral, and reassemble.